R E S E A R C H A R T I C L E

Contrasting e¡ectsofwoodashapplicationonmicrobialcommunitystructure,biomass and processes in drained forestedpeatlandsRobert G. Bjork1,2, Maria Ernfors2, Ulf Sikstrom3, Mats B. Nilsson4, Mats X. Andersson2, Tobias Rutting2 &Leif Klemedtsson2

1School of Science and Technology, Orebro University, Orebro, Sweden; 2Department of Plant and Environmental Sciences, University of Gothenburg,

Gothenburg, Sweden; 3The Forestry Research Institute of Sweden (Skogforsk), Uppsala, Sweden; and 4Department of Forest Ecology and Management,

Swedish University of Agricultural Sciences (SLU), Umea, Sweden

Correspondence: Robert G. Bjork,

Department of Plant and Environmental

Sciences, University of Gothenburg, PO Box

461, SE-405 30 Gothenburg, Sweden. Tel.:

146 704 54 65 41; fax: 146 31 786 2560;

e-mail: robert.bjork@dpes.gu.se

Received 12 November 2009; revised 8 April

2010; accepted 5 May 2010.

Final version published online 9 June 2010.

DOI:10.1111/j.1574-6941.2010.00911.x

Editor: Philippe Lemanceau

Keywords

methane; microbial response; nitrogen

turnover; peat; PLFA; substrate-induced

respiration (SIR).

Abstract

The effects of wood ash application on soil microbial processes were investigated in

three drained forested peatlands, which differed in nutrient status and time since

application. Measured variables included the concentrations of soil elements and

phospholipid fatty acids (PLFAs), net nitrogen (N) mineralization, nitrification

and denitrification enzyme activity, potential methane (CH4) oxidation, CH4

production and microbial respiration kinetics. Wood ash application had a

considerable influence on soil element concentrations. This mirrored a decrease

in the majority of the microbial biomarkers by more than one-third in the two

oligotrophic peatlands, although the microbial community composition was not

altered. The decreases in PLFAs coincided with reduced net ammonification and

net N mineralization. Other measured variables did not change systematically as a

result of wood ash application. No significant changes in microbial biomass or

processes were found in the mesotrophic peatland, possibly because too little time

(1 year) had elapsed since the wood ash application. This study suggests that

oligotrophic peatlands can be substantially affected by wood ash for a period of at

least 4 years after application. However, within 25 years of the wood ash

application, the microbial biomass seemed to have recovered or adapted to

enhanced element concentrations in the soil.

Introduction

Concerns over climate change are driving changes in legisla-

tion, as well as creating incentives for and commercialization

of renewable energy sources. For example, the European

Union has proposed increasing the share of renewable sources

within its overall energy generation to 20% by 2020 (EU,

2007). A byproduct of the increased use of biofuels for energy

production is the generation of large amounts of wood ash.

In Sweden, about 1.3 million tonnes of ash are produced

annually, of which about 250 000–300 000 tonnes originate

from biofuels, for example forest residues (Bjurstrom et al.,

2003). Apart from being a potential ameliorative treatment,

i.e. it can compensate for soil acidification and a large export

of nutrients after intensive forest harvest (e.g. whole-tree

harvest), the wood ash can also be used as a fertilizer to

increase tree growth on drained peat soils (e.g. Moilanen

et al., 2004, 2005). Tree growth in boreal forests on mineral

soils is generally limited by plant-available nitrogen (N) (e.g.

Tamm, 1991), whereas growth on organic soils is often

limited by phosphorus (P) or potassium (K) (Paavilainen &

Paivanen, 1995). Wood ash contains all the elements needed

for tree growth, except N, which only occurs in trace amounts

(Vance, 1996; Demeyer et al., 2001). Nutrient compensation

in the form of wood ash, for the brash removal at whole-tree

harvest, which commonly corresponds to doses of c.

1–3 tonnes wood ash ha�1, is probably more important on

peatlands than on mineral soils, because mineral nutrients in

peatlands, such as P and K, are not supplied by the weath-

ering of minerals (Magnusson & Hanell, 1996).

In addition to supplying nutrients, wood ash application

has a high acid-neutralizing capacity in soils, due to the

FEMS Microbiol Ecol 73 (2010) 550–562c� 2010 Federation of European Microbiological SocietiesPublished by Blackwell Publishing Ltd. All rights reserved

MIC

ROBI

OLO

GY

EC

OLO

GY

formation of hydroxides and carbonates during the combus-

tion and conditioning processes (Steenari et al., 1999; Holm-

berg & Claesson, 2001). The application of wood ash, with

pH values ranging from 8 to 13 (Augusto et al., 2008), thus

increases the soil pH, which in turn affects the solubility of the

elements in the soil (Augusto et al., 2008) and increases the

cation exchange capacity and base saturation of the soil

(Bramryd & Fransson, 1995; Saarsalmi et al., 2001, 2004).

Few studies on the effects of wood ash addition on soil

microbial processes have been conducted on organic soils.

In a recent meta-analysis, Augusto et al. (2008) surveyed the

effects of wood ash on forest ecosystems and found that the

biogeochemical cycles in peatland soils appeared to be

considerably modified for many years following wood ash

addition. For instance, application of wood ash increased

the activity and modified the community composition of

microorganisms, with implications for microbial processes

and nutrient cycling. Jokinen et al. (2006) reported an

increase in the amount and quality of dissolved organic

carbon (DOC), as an effect of the increase in pH after wood

ash application. Both increased pH and DOC quality

affected the bacterial community by favouring a restricted

number of microbial groups and increasing microbial

activity (Jokinen et al., 2006). The few studies that exist on

carbon (C) mineralization in ash-amended soils have been

conducted on mineral soils and have reported an increase in

carbon dioxide (CO2) evolution rates (Baath & Arnebrant,

1994; Fritze et al., 1994; Baath et al., 1995). Studies on the

effects of wood ash application in forests on N mineraliza-

tion, mostly also conducted on mineral soils, are inconclu-

sive; both unaffected and increased N mineralization rates

have been reported (Karltun et al., 2008). Peat soils can

potentially emit large amounts of the greenhouse gases

(GHGs) CO2, methane (CH4) and nitrous oxide (N2O)

(Maljanen et al., 2009), but few studies have been published

on GHG fluxes after wood ash fertilization of drained peat

soils (Silvola et al., 1985; Maljanen et al., 2006; Ernfors,

2009; Klemedtsson et al., in press). However, these studies

are not conclusive, having shown decreased emissions

(Maljanen et al., 2006; Klemedtsson et al., in press), no

effect (Maljanen et al., 2006; Ernfors, 2009) and slightly

increased (Silvola et al., 1985; Maljanen et al., 2006) GHG

emissions after wood ash application. Therefore, a better

understanding of the effects of wood ash applications on

drained forested peatland soils is of major importance. As

noted by Augusto et al. (2008), there are insufficient data

available on wood ash effects on soil processes in drained

forested peatlands to be able to provide any general recom-

mendations on management practices. The potential for

drained peatlands to emit large amounts of GHGs and the

lack of adequate data highlight the need to investigate the

effects of wood ash application on these soil systems, before

large-scale use.

The general objective of this study was to determine the

effects of wood ash application on drained forested peat-

lands, with respect to the microbial community structure

and biomass, microbial processes and abiotic properties in

the top 30 cm of the peat soil, because these control the

GHG fluxes from the soil. The study addresses the effects of

the application of 2.5–3.3 tonnes wood ash ha�1 at three

drained forested peatlands that differed in nutrient status

and time since application.

Materials and methods

Study sites

The study was conducted at three drained forested peatlands

in Southern Sweden, Perstorp (oligotrophic), Anderstorp

(oligotrophic) and Skogaryd (mesotrophic; Table 1). Site

fertility was defined based on the soil C/N ratio (see Table 2)

and according to the classification proposed by Succow &

Joosten (2001). The Perstorp site is a poorly drained bog.

When the experiment was established in 1982, the tree layer

was dominated by 1.3-m-tall Scots pine (Pinus sylvestris L.)

trees and also contained some Downy Birch (Betula pub-

escens Ehrh.) of similar height. The stem volume incre-

ment in the control plots from 1982 to 2007 was almost

negligible (approximately 0.04 m3 of stemwood ha�1 year�1).

During the same period, the annual volume increment in

the plots treated with wood ash was 1.6 m3 ha�1 year�1,

which resulted in a sixfold higher standing stem volume

in the wood ash plots (48 m3 ha�1) compared with the

control plots (7.4 m3 ha�1) in 2007 (Sikstrom et al., in press).

The experimental site at Anderstorp is a well-drained bog

and the tree stand was thinned in the late 1980s. The stem

volume of the tree stand at Anderstorp was 110 m3 ha�1

when the experiment was established (Ernfors, 2009). The

Skogaryd experimental site is a well-drained forested mire.

The standing tree stem volume when the experiment was

established was 400 m3 ha�1 (Klemedtsson et al., in press).

Additional site characteristics are given in Table 1.

Experimental design

The experiments followed a randomized block design. At

each experimental site, three or four blocks were established

based on understorey vegetation and cover, number of trees

and tree basal area (1.3 m above the ground). The treatments

were randomly allocated to the plots within each block. The

element concentrations in the wood ashes used at each

experimental site are described in Sikstrom et al. (2009),

and more details on the experimental design are given in

Table 1.

FEMS Microbiol Ecol 73 (2010) 550–562 c� 2010 Federation of European Microbiological SocietiesPublished by Blackwell Publishing Ltd. All rights reserved

551Wood ash effects on drained forested peatlands

Soil sampling

All three experimental sites were sampled in November 2007

by taking a total of 10 soil cores from two transects, of five

samples each, within each experimental plot. Soil cores were

taken to a depth of 30 cm, excluding the litter layer. All

samples were divided into three depths (0–5, 5–20 and

20–30 cm) and each depth was subsequently divided verti-

cally into three parts. The first and second parts of the

samples for each depth were placed in separate bags for the

determination of bulk density and CH4 production, respec-

tively. The remaining parts were mixed to form a combined

sample for each experimental plot and depth and were

sieved (4 mm mesh size) within 2 days of sampling. Sub-

samples from all three soil depths were analysed for pH,

C : N ratio, element concentrations and amounts of ammo-

nium lactate-extractable P and K. From the depths 0–5 and

20–30 cm, additionally, phospholipid fatty acid (PLFA)

concentration, net N mineralization, nitrification enzyme

activity (NEA), denitrification enzyme activity (DEA),

potential CH4 oxidation and microbial respiration kinetics

were measured. All samples were kept at 14 1C, both before

and after subsampling, except for the subsamples for PLFA

analysis, which were frozen (� 18 1C) until further analysis.

Chemical and physical soil characteristic

Soil pH was measured for fresh soil : water suspensions

(1 : 10 by weight), which had been shaken for 1 h and left to

settle overnight at room temperature. The combined soil

samples were then dried at 80 1C for 48 h and subsamples for

the analyses of total C and N, other total element contents

and plant-available P and K were ground to a fine powder.

The total C and N contents were determined by combustion

in an elemental analyser (Model: EA 1108 CHNS-O, Fison,

Italy). For the other elemental analyses, samples of 0.5 g were

digested in hot (4 95 1C) Aqua Regia for 1 h. After cooling,

the solution was made up to the final volume with 5% HCl

(sample weight to solution volume: 1 g per 20 mL) and

analysed by inductively coupled plasma-MS (ICP-MS;

Table 1. Site and experimental design description of the experiments at Anderstorp, Perstorp and Skogaryd

Anderstorp Perstorp Skogaryd

Site characteristics

Location 571150N, 131350E 561120N, 131170E 58123 0N, 121090E

Drainage In the late 1980s In 1981 In the 1870s

Plant community classification� Wooded bog of the dwarf

shrubtype with pine

Heather-Sphagnum magellanicum-

type

Spruce forest of low herb type

Tree species (%) Pine 99 – Spruce 1 – Birch 0 Pine 100 – Spruce 0 – Birch 0 Pine 2 – Spruce 95 – Birch 3

Understorey vegetation Vaccinium myrtillus L. Calluna vulgaris (L.) Hull Vaccinium myrtillus L.

Vaccinium vitis-idaea L. Erica tetralix L. Luzula pilosa (L.) Willd.

Eriophorum vaginatum L. Eriophorum vaginatum L. Oxalis acetosella L.

Deschampsia flexuosa (L.) Trin.,

Dryopteris carthusiana (Vill.) H. P.

Fuchs

Mycelis muralis (L.) Dumort.

Bryophyte vegetation Pleurozium schreberi (Willd. ex

Brid.) Mitt.

Sphagnum capillifolium (Ehrh.)

Hedw.

Pleurozium schreberi (Willd. ex

Brid.) Mitt.

Aulacomnium palustre (Hedw.)

Schwagr.

Sphagnum magellanicum Brid. Dicranum majus Sm.

Dicranum polysetum Sw. ex anon. Hypnum cupressiforme Hedw. Hylocomium splendens (Hedw.)

Schimp.

Pleurozium schreberi (Willd. ex

Brid.) Mitt.

Plagiomnium affine (Blandow ex

Funck) T.J.Kop.

Mylia anomala (Hook.) Gray Polytrichastrum formosum (Hedw.)

G.L.Sm.

Sciuro-hypnum oedipodium (Mitt.)

A.Jaeger.

Experimental design

Number of replicates Four blocks Four blocks Three blocks

Wood ash addition

(tonnes d.w. wood ash ha�1)

0 and 3.3 0 and 2.5 0 and 3.3

Type of wood ash Crushed wood ash Loose wood ashw Crushed wood ash

Date of wood ash application 5–6 September 2003 29 June 1982 7–8 August 2006

�According to Pahlsson (1998).wThere is no information on the type of wood ash that was used, but it is likely to have been a loose wood ash.

FEMS Microbiol Ecol 73 (2010) 550–562c� 2010 Federation of European Microbiological SocietiesPublished by Blackwell Publishing Ltd. All rights reserved

552 R.G. Bjork et al.

Perkin Elmer Elan 6000/9000). For analysis of plant-avail-

able P and K, 5 g of dried and ground soil was shaken with

100 mL of ammonium lactate solution (0.10 mol ammo-

nium lactate and 0.40 mol acetic acid) for 90 min at room

temperature. The samples were filtered (Munktell V00A

filter paper, Stora AB, Grycksbo, Sweden) and analysed by

ICP (Perkin Elmer Optima 3000 DV). The volumetric

samples were dried for 48 h at 80 1C and the dry weight

(d.w.) of each sample was used to calculate the bulk density.

The soil water content (% d.w.) was calculated from the

same samples as the difference between their dry and wet

weights. The soil organic matter (SOM; % d.w.) content was

defined as the weight loss of subsamples of the dried

combined samples, after 6 h of heating at 550 1C.

Microbial community structure and biomass

The composition and biomass of the soil microbial commu-

nity were determined using the PLFA technique, following

Frostegard et al. (1993), with minor modifications of the

extraction procedure. Thawed soil samples (1–2 g) were

extracted as described, with di-nonadecanoyl phosphatidyl-

choline (Larodan, Sweden) added as an internal standard.

The phospholipids were transesterified with 0.5 M sodium

methoxide and the methyl esters were analysed on a gas

chromatograph equipped with a DB-5 capillary column

(30 m� 0.25 mm, J&W Scientific) and a flame ionization

detector. Standard notation is used to describe PLFAs

(Frostegard et al., 1993). The relative proportions of PLFAs

(mol%) were used to describe the microbial community

composition (Frostegard et al., 1993). Molar amounts

[nmol g�1 organic matter (OM)] of the total and individual

PLFAs were used as an estimate of microbial biomass

(Frostegard & Baath, 1996). The ratio of fungi to bacteria

(F : B ratio) was calculated based on the total molar amount

of 18:2o6,9 (indicating fungal PLFA), and i-15:0, a-15:0,

15:0, i-16:0, 16:1, cy17:0, 10Me-16:0, i-17:0, a-17:0, 18:1o7,

10Me-18:0 and cy19:0 (indicating bacterial PLFA; Zak et al.,

1996). The bacterial PLFA were further divided into bio-

markers for gram-negative bacteria (cy-17:0, 18:1o7 and

cy-19:0) and for gram-positive bacteria (i-15:0, a-15:0,

i-16:0, 10Me-16:0, i-17:0, a-17:0 and 10Me-18:0). PLFAs

10Me-16:0 and 10Me-18:0 were used as biomarkers for

actinobacteria (Kroppenstedt, 1985).

Net N mineralization analysis

Net N mineralization was determined according to Robert-

son et al. (1999), with minor modifications. From each

general sample, six subsamples of about 10 g fresh soil were

Table 2. Characteristics of the soil in experiments at Anderstorp (n = 4), Perstorp (n = 4) and Skogaryd (n = 3)

Soil depth (cm)

pH SOM (%) C/N Bulk density (g dm�3)

Controlw Wood ashz Control Wood ash Control Wood ash Control Wood ash

Anderstorp

0–5 4.9 5.1 96.2 93.4 34.2 34.4 97.3 86.3

(0.3) (0.3) (0.2) (1.8) (1.0) (1.6) (5.1) (9.4)

5–20 4.8 4.9 96.3 96.4 35.8 35.6 118.8 117.0

(0.1) (0.1) (0.1) (0.2) (0.5) (2.0) (8.9) (13.3)

20–30 4.7 4.8 97.7 97.8 42.5 42.9 133.4 123.6

(0.1) (0.1) (0.2) (0.1) (2.2) (2.4) (19.2) (22.0)

Perstorp

0–5 4.9 5.1 95.0 94.5 29.9 31.2 96.0 98.9

(0.1) (0.3) (0.2) (0.6) (0.6) (1.1) (13.0) (9.1)

5–20 5.1 4.8 96.1 95.9 38.6 37.9 113.2 107.6

(0.2) (0.2) (0.1) (0.2) (1.1) (0.7) (15.6) (6.3)

20–30 4.8 4.9 98.1 98.0 47.5 45.5 97.9 93.8

(0.2) (0.1) (0.2) (0.2) (2.2) (2.3) (9.1) (9.0)

Skogaryd

0–5 4.5 5.0� 79.4 75.4 23.1 23.4 194.7 189.0

(0.1) (0.1) (9.6) (11.2) (1.0) (0.8) (40.4) (13.3)

5–20 4.4 4.5 78.6 73.3 24.8 26.3 263.6 297.4

(0.1) (0.2) (10.2) (16.3) (0.5) (2.4) (28.9) (63.9)

20–30 4.6 4.4 89.8 88.0 29.6 32.3 210.2 209.9

(0.1) (0.2) (3.5) (6.5) (2.3) (1.6) (16.6) (23.5)

Significant differences (Po 0.05) between the mean values (� SE) of treatments are denoted by:�Po 0.05. wControl, untreated control. zWood ash, 2.5 tonnes d.w. unknown wood ash ha�1 in Perstorp; 3.3 tonnes d.w. crushed wood ash ha�1 in

Anderstorp and Skogaryd.

FEMS Microbiol Ecol 73 (2010) 550–562 c� 2010 Federation of European Microbiological SocietiesPublished by Blackwell Publishing Ltd. All rights reserved

553Wood ash effects on drained forested peatlands

weighed into plastic bottles. Half of the subsamples were

extracted immediately in 70 mL 1 M KCl. To determine net

N mineralization, net ammonification and net nitrification,

the remaining subsamples were incubated in the dark for 28

days and then extracted with 1 M KCl. Soil-extractable NO3�

and NH41 were analysed using a flow injection analyser

(Tecator 5010, Hoganas, Sweden). Net ammonification and

net nitrification were calculated as the difference in extrac-

table NH41 and NO3

� values before and after incubation. Net

N mineralization was estimated as the sum of net ammoni-

fication and net nitrification.

NEA

A two-step incubation technique was used to determine

NEA (Lensi et al., 1985, 1986), as described in detail by Bjork

et al. (2007), for analysing low nitrification rates in acidic

soils. In short, the fresh soil was first incubated in the dark at

room temperature for 24 h in a nutrient solution on a rotary

shaker. Subsamples were taken at specified times. In the

second step, NO3�was reduced to N2O by adding a modified

denitrifying bacterium, Pseudomonas chlororaphis ATCC

43928, together with a C source. This strain of bacteria lacks

the enzyme to reduce N2O to N2. The samples were then

incubated again in the dark at room temperature for 24 h,

and headspace N2O concentrations were analysed by GC

(Klemedtsson et al., 1997).

DEA

The following anaerobic incubation technique, based on

acetylene inhibition of the N2O-reductase, was used to

determine DEA (Klemedtsson et al., 1977; Smith & Tiedje,

1979), and is described in detail by Bjork et al. (2007). Fresh

soil was incubated at 20 1C in a nutrient solution under

anaerobic conditions (9 : 1 v/v mixture of N2 and acetylene),

while being continuously shaken. At specific time intervals

during incubation, gas samples were taken and analysed by

GC (Klemedtsson et al., 1997).

Potential CH4 oxidation

Samples of about 10 g fresh soil were added to 300-mL flasks

sealed with air-tight lids fitted with gas sampling septum.

The flasks were filled with 25 mL of distilled water; the

headspace was evacuated and then filled with CH4 and air to

yield a final CH4 concentration of 500 mL L�1 (Sundh et al.,

1994; Moore & Dalva, 1997). Subsequently, the samples

were incubated for 15 h in the dark at room temperature

while being shaken continuously. At specific time intervals

during incubation, gas samples were taken using an airtight

syringe. CH4 concentrations were analysed on a gas chro-

matograph (Klemedtsson et al., 1997) and CH4 oxidation

rates were estimated by linear regression. Only regressions

with r24 0.90 were included in the analysis.

CH4 production

Each incubation bottle was filled with 50 mL of deionized

water (Millipore MQ) and autoclaved. The soil samples were

homogenized manually and 10 small randomly selected

portions of the soil, totalling 15–20 g fresh weight, were

transferred to the bottles. The bottles were evacuated,

flushed with N2 and incubated in the dark at room

temperature for 5 days. One hour before gas sampling, the

bottles were placed on a rotary shaker (Bergman et al.,

1998). Gas samples were taken once every day and analysed

by GC (Klemedtsson et al., 1997). The CH4 production

rates were determined by linear regression, excluding

the first data point in the time series due to initial dis-

turbance. Only regressions with r24 0.90 were included in

the analysis.

Microbial heterotrophic respiration kinetics andmicrobial biomass

To describe the heterotrophic microbial community, the

following kinetic parameters were estimated from oxic

incubations of soil samples, following Nordgren (1988): (1)

basal respiration (BR) – CO2 production without amend-

ments; (2) substrate-induced respiration (SIR) – CO2 pro-

duction after amendment with glucose; (3) lag time – time

between substrate addition and the start of exponential

growth of the microorganisms; and (4) exponential growth

rate. In addition to these parameters, the amounts of

microbially available N and P were determined (Nordgren,

1992). Samples containing about 1 g OM were weighed into

250-mL plastic jars. Before the incubation, the water content

was adjusted to 60% of the water-holding capacity. The

incubation jars were kept in the dark, in a water bath at a

constant temperature of 120 1C (� 0.1 1C) and soil respira-

tion was measured hourly using a respirometer (Respicond

IV; A. Nordgren Innovations, Djakneboda, Sweden; Nordg-

ren, 1988, 1992).

Once the respiration had stabilized, hourly measurements

were taken for 40 h. The average of these was considered to

represent the BR. To estimate SIR, lag time and exponential

growth, samples were amended after the 40-h period with a

mix of glucose, nitrogen [(NH4)2SO4] and phosphorus

(KH2PO4). The estimation of microbially available N and P

was based on the addition of glucose plus P and the addition

of glucose plus N, respectively. These estimates were based

on the assumption that exponential growth stops when the

excluded nutrient, N or P, becomes limiting (Nordgren,

1992). SIR was also used to estimate the microbial biomass

(Anderson & Domsch, 1978).

FEMS Microbiol Ecol 73 (2010) 550–562c� 2010 Federation of European Microbiological SocietiesPublished by Blackwell Publishing Ltd. All rights reserved

554 R.G. Bjork et al.

Statistical analysis

The overall effect of wood ash application on soil element

concentrations was investigated using a MANOVA, with site,

treatment and soil depth as fixed factors. Thereafter, a

principal component analysis (PCA) on element concentra-

tions was conducted, using CANOCO 4.5 to investigate the

specific changes in soil chemistry for sites and soil depth.

PCA was also used to examine the relative proportion of

PLFAs (mol%) in order to identify changes in the microbial

community composition. To test for the significant effects of

wood ash application on the microbial community compo-

sition and soil chemistry, the sample scores for principal

components (PC) 1 and 2 for each PCA were used as input

variables in a one-way ANOVA, with treatment as a fixed

factor. The effect of wood ash application on the other

variables, including molar amounts of the PLFAs, was

analysed individually for each soil depth and site using a

MANOVA, with treatment as a fixed factor. All data, except

PLFAs (%), were, after the addition of a constant, log-

transformed and concomitantly scaled to unit variance to

achieve a normal distribution and to eliminate skewness and

ensure homogeneity of variances according to Økland et al.

(2001).

Results

Chemical and physical soil characteristics

The MANOVA showed a significant treatment effect

(Po 0.001) on the soil element concentrations, but also a

significant interaction (P = 0.041) between site, treatment

and soil depth. In the PCA of the element concentrations,

the eigenvalues were 0.91 for PC 1 and 0.06 for PC 2,

explaining 97% of the total variance. Along PC 1, significant

differences (P � 0.004) between controls and treated plots

were found at all depths at Perstorp, whereas at Anderstorp,

significant differences (P = 0.048) occurred only in the top

soil (0–5 cm) (data not shown). At Skogaryd, there were no

significant differences between treatments along PC 1 (data

not shown). Along PC 2, no significant differences were

found in any of the experiments (data not shown). At

Skogaryd, the pH in the top soil (0–5 cm) was significantly

(P = 0.027) higher (0.5 U) in the plots treated with wood ash

compared with the control plots (Table 1). At the other two

sites, no changes in pH were detected. The SOM content,

C : N ratio and bulk density were not affected by wood ash

application at any of the sites (Table 2). The amount of

ammonium lactate-extractable P was significantly

(P = 0.016) higher (66%) in the top soil (0–5 cm) at Ander-

storp and, at Skogaryd, was 58% greater in the wood ash-

treated plots (0–5 cm) compared with the control plots

(although not significantly so, P = 0.058). There were no

significant changes in the amounts of ammonium lactate-

extractable K, as a result of wood ash application.

Microbial community structure and biomass

The microbial community structure, measured as the rela-

tive proportions of PLFAs, did not show any significant

difference in sample scores along the first two PC axes

associated with the addition of wood ash (Fig. 1). However,

some patterns in the PCA could still be discerned. The top

soil layer (0–5 cm) in the wood ash-treated plots at Perstorp

tended to group more closely with top soils (0–5 cm) from

Anderstorp (Fig. 1). This grouping was associated with an

increased occurrence of the PLFAs i15:0, a15:0, 16:0, 16:1

and 18:2o6,9. The 20–30-cm layers, including all controls

and ash-treated plots, at Anderstorp and Perstorp grouped

together with the control plots of the top layer (0–5 cm)

from Perstorp (Fig. 1). The grouping was related to an

increase in the PLFAs 10Me-18:0, 18:0 and 18:1o9. There

was also a distinction between Skogaryd and the other two

sites (Fig. 1), in that there was a higher content of the PLFAs

10Me-16:0, i16:0, i17:0, a17:0, cy17:0 and cy19:0 at Skogaryd,

irrespective of treatment.

Despite the lack of a significant change in the microbial

community structure, i.e. the relative proportions of PLFAs,

as revealed by the ANOVA of the PC sample scores, there were

some significant differences between the molar amounts of

the different PLFA markers or groups of markers (Fig. 2).

This reflects changes in microbial biomass among these

groups. In the 20–30-cm layer at the Perstorp site, addition

of wood ash caused a significant decrease in the absolute

amount of total PLFAs and in the PLFAs specific to gram-

positive bacteria by 34% and 40%, respectively (Fig. 2a and e).

Fig. 1. Mean values (�85% confidence interval corresponding to a

a= 0.05 test; see Payton et al., 2000, 2003) of sample scores from the

PCA, comparing the relative abundances of PLFA (mol%) profiles for

control plots (circles) and plots treated with wood ash (triangles) in the

experiments at Anderstorp (n = 4), Perstorp (n = 4) and Skogaryd (n = 3).

The eigenvalues are 0.35 for PC 1 and 0.24 for PC 2. Of the total

variance, 35% is explained by PC 1 and 24% by PC 2, together

explaining 59% of the total variance.

FEMS Microbiol Ecol 73 (2010) 550–562 c� 2010 Federation of European Microbiological SocietiesPublished by Blackwell Publishing Ltd. All rights reserved

555Wood ash effects on drained forested peatlands

Among the gram-positive bacteria, a significant decrease

(39%) in actinobacteria was detected (Fig. 2c). A nonsigni-

ficant tendency (P = 0.108) towards a decrease (44%) in the

fungal biomarker (18:2o6,9) was also found at the 20–30-

cm layer in the wood ash treatment compared with the

control (Fig. 2d). At Anderstorp, there was a significant

decrease in the fungal biomarker by 44% in the top soil

(0–5 cm), where wood ash had been applied (Fig. 2d).

Furthermore, the biomarkers for gram-negative bacteria

(P = 0.083) and actinobacteria (P = 0.107) exhibited non-

significant tendencies to decrease (by 44% and 30%, respec-

tively) in the wood ash treatment at Anderstorp (Fig. 2b and

c). No other statistically significant differences in microbial

biomass were found (Fig. 2; Table 2), including the micro-

bial biomass, as assessed using the SIR method.

Microbial processes

There were no significant changes in BR after wood ash

application (Table 3). In Perstorp, the exponential growth

rate in the 20–30 cm soil depth was significantly lower

(P = 0.028) in the wood ash-treated plots compared with

the controls, whereas a tendency (P = 0.096) towards in-

creased rates was found in the top soil (0–5 cm) at Ander-

storp (Table 3). No other changes in the exponential growth

rate were observed. Lag time and microbially available N and

P did not show any significant changes due to the wood ash

application (Table 3). Net N mineralization decreased sig-

nificantly by 4 80% and 4 40% in the wood ash treat-

ments at Anderstorp (0–5 cm) and Perstorp (20–30 cm),

respectively (Fig. 3c). The decreases in net N mineralization

Fig. 2. Molar amounts of PLFAs (nmol g�1 OM) for gram-positive bacteria (a), gram-negative bacteria (b), actinobacteria (c), fungi (d), the total amount

of PLFA (e) and the F : B ratio (f) in experiments Anderstorp (n = 4), Perstorp (n = 4) and Skogaryd (n = 3). Error bars represent SEs of the means. Values

were considered to be significantly different if Po 0.05; NS, not significant. Treatments: control plots (white bars), plots treated with wood ash plots

(grey bars). A, Anderstorp; P, Perstorp; S, Skogaryd; 0–5, soil depth 0–5 cm; 20–30, soil depth 20–30 cm.

FEMS Microbiol Ecol 73 (2010) 550–562c� 2010 Federation of European Microbiological SocietiesPublished by Blackwell Publishing Ltd. All rights reserved

556 R.G. Bjork et al.

were mainly a consequence of significant decreases in net

ammonification (Fig. 3a). At Skogaryd, the net ammonifica-

tion showed a 75-fold nonsignificant decrease (P = 0.084) in

the wood ash treatments at the 0–5-cm layer, but the

ammonification rates were low (Fig. 3a). NEA, DEA,

potential CH4 oxidation and CH4 production were not

affected by the wood ash application, except in the top soil

(0–5 cm) at Anderstorp, where DEA exhibited a nonsignifi-

cant decrease (P = 0.071) by 50% in the wood ash-treated

plots (Table 4).

Discussion

Wood ash application had a considerable effect on the

element composition of the soils from the drained oligo-

trophic peatlands, Anderstorp and Perstorp. This was re-

lated to the time elapsed since the application, even though

the two sites differed in forest stand volume and drainage

status. In Anderstorp, 4 years after wood ash application,

most of the significant increases in element concentrations

were detected in the top soil (0–5 cm), whereas in Perstorp,

25 years after treatment, most changes were apparent deeper

in the peat (5–30 cm). This most likely reflects the time it

takes for the wood ash to dissolve and move downwards

through the peat soil. Studies of the effect of lime on mineral

soils have demonstrated a downward transport time

through the soil of 1 cm year�1 (Persson et al., 1990). At the

more fertile site, Skogaryd, 1 year had elapsed since wood

ash application and no general effect on the element

composition of the soil was found, although pH was 0.5 U

greater in the top soil (0–5 cm) in the wood ash-amended

plots compared with the control. In reviewing three studies

on organic soils, Augusto et al. (2008) reported a large effect

of wood ash addition on soil pH (up to 11.5 pH U), but the

sparse data available for organic soils were insufficient to

perform a meta-analysis. On the other hand, Galand et al.

(2005) did not find any significant increase in pH on a

drained mire in Finland 5 years after ash application

(15 tonnes loose ash ha�1), which is in agreement with the

data from our oligotrophic sites. In our study, the effect of

wood ash on element composition in the soil was still

detectable in the top soil (0–5 cm) at Perstorp 4 25 years

after the application. Many of the elements present in wood

ash can be retained in the humus layers in mineral soils, as a

result of decreased mobility due to the pH increase (Bram-

ryd & Fransson, 1995). However, in our study, only Skogar-

yd showed an increased pH after wood ash application. The

increased element concentration is, therefore, likely to be a

result of remaining undissolved wood ash and the formation

of complexes with the organic material.

Table 3. Microbial respiration in experiments at Anderstorp (n = 4), Perstorp (n = 4) and Skogaryd (n = 3)

BR SIR m Lag timew Microbial N Microbial P

(mg CO2 g�1 OM h�1) (mg CO2 g�1 OM h�1) (h�1) (h) (mg N g�1 OM) (mg P g�1 OM)

Soil depth

(cm) ControlzWood

ash‰ Control

Wood

ash Control

Wood

ash Control

Wood

ash Control

Wood

ash Control

Wood

ash

Anderstorp

0–5 0.046 0.053 0.171 0.211 0.142 0.163# 6.80 6.59 – – – –

(0.001) (0.004) (0.013) (0.026) (0.010) (0.004) (0.88) (0.52)

20–30 0.014 0.012 0.026 0.027 0.142 0.142 6.80 8.36 – – – –

(0.003) (0.004) (0.002) (0.002) (0.010) (0.008) (0.88) (1.62)

Perstorp

0–5 0.058 0.063 0.146 0.221 0.132 0.146 10.61 6.61 – – – –

(0.008) (0.014) (0.014) (0.032) (0.006) (0.006) (2.75) (0.50)

20–30 0.013 0.014 0.045 0.041 0.167 0.137� 7.91 8.67 – – – –

(0.003) (0.002) (0.005) (0.009) (0.007) (0.007) (0.59) (2.75)

Skogaryd

0–5 0.028 0.043 0.075 0.107 0.126 0.124 12.97 13.15 3.81 4.31 1.69 1.18

(0.006) (0.008) (0.016) (0.021) (0.007) (0.008) (0.05) (0.12) (0.75) (0.50) (0.45) (0.19)

20–30 0.012 0.011 0.020 0.019 0.130 0.124 19.16 18.17 7.91 9.30 6.63 4.20

(0.001) (0.003) (0.003) (0.005) (0.019) (0.016) (2.20) (2.21) (0.47) (1.36) (2.26) (0.42)

Significant differences (Po 0.05) between the mean values (� SE) of treatments are denoted by:#Po 0.10 and �Po 0.05. wLag time (h) was measured as time between substrate addition and the start of exponential growth of the microorganisms.zControl, untreated control. ‰Wood ash, 2.5 tonnes d.w. unknown wood ash ha�1 in Perstorp; 3.3 tonnes d.w. crushed wood ash ha�1 in Anderstorp and

Skogaryd.

m, microbial growth rate; lag time, the time it takes before the microbial growth starts; Microbial N, microbially available N; Microbial P, microbially

available P.

FEMS Microbiol Ecol 73 (2010) 550–562 c� 2010 Federation of European Microbiological SocietiesPublished by Blackwell Publishing Ltd. All rights reserved

557Wood ash effects on drained forested peatlands

Application of wood ash caused decreases in the absolute

amounts of PLFAs in the oligotrophic peatlands at Ander-

storp and Perstorp. The decrease in PLFAs was also related

to time since wood ash application, with the effect moving

deeper down the soil profile over time. Interestingly, in the

top soil at Perstorp, no significant changes in the amounts of

PLFAs were found, although the soil chemistry was affected

by the wood ash application. This suggests that the micro-

bial community had recovered or adapted to the modified

element concentrations in the soil. However, the decrease in

the total amount of PLFAs found was not reflected in the

SIR. Fungi have been shown to contribute most to SIR in a

variety of ecosystems (Lin & Brookes, 1999; Susyan et al.,

2005). Recently, in a 13C-PLFA-stable isotope probing

experiment, Rinnan & Baath (2009) showed that fungi

played a greater role in the use of glucose compared with

bacteria. This may explain the lack of response in SIR in our

experiment, as the F : B ratio in our study was very low

(0.02–0.20) and, hence, the glucose addition stimulated only

a small fraction of the total microbial biomass. Earlier

studies on mineral soils (Fritze et al., 1994; Baath et al.,

1995; Perkiomaki & Fritze, 2002) showed that wood ash

application had changed both the microbial activity and the

community structure in the humus layer, although the effect

was dependent on both the dose and the type of wood ash

applied. However, no short-term studies with wood ash

doses in our range, 2.5–3.3 tonnes wood ash ha�1, have

shown any effects on the microbial biomass, although

several techniques have been applied, including fumigation–

extraction (Fritze et al., 1994), PLFA (Baath et al., 1995;

Perkiomaki & Fritze, 2002) and SIR (Baath & Arnebrant,

1994; Fritze et al., 1994; Perkiomaki & Fritze, 2002). At a

Podzol afforested with Scots pine, Perkiomaki & Fritze

(2002) reported an increased BR in the humus layer 18 years

after the addition of loose wood ash (3.3 tonnes wood

ash ha�1). Although they were able to show a shift in the

microbial community structure, they did not identify any

changes in microbial biomass (measured as the total molar

amount of PLFAs). Furthermore, in a boreal peatland,

Makiranta et al. (2009) reported that drought stress de-

creased the total microbial biomass (measured as the molar

amount of PLFAs) in the surface peat layer, leading to a

reduced peat decomposition rate when the water table

reduced to a depth below 60 cm. In Anderstorp, a tendency

towards increased tree production and a lowered water table

during summer 2008 was reported to be an effect of wood

ash application (Ernfors, 2009). During this period, when

the water consumption by the trees was at its greatest, the

ground water table declined below the critical 60-cm level

reported by Makiranta et al. (2009). This low water table

may have caused drought at the surface and may explain the

observed decrease in the amounts of PLFAs throughout the

soil profile, as an indirect effect of the wood ash application.

However, at Perstorp, drought cannot explain the decrease

in the amount of PLFAs, as this was only found at a soil

depth of 20–30 cm. Furthermore, the bog at Perstorp is

poorly drained, with plant growth in the ditches and a water

table that is only occasionally below a depth of 30 cm

(Sikstrom et al., in press). Even though the amounts of

PLFAs decreased in our study, we did not find any changes

in the microbial community structure (relative proportion

of PLFA profiles) due to the wood ash treatment. Previous

studies on mineral soils have suggested that pH is the most

important abiotic variable that drives microbial processes

Fig. 3. Net ammonification (a), net nitrification (b) and net N miner-

alization (c) in experiments Anderstorp (n = 4), Perstorp (n = 4) and

Skogaryd (n = 3). Error bars represent the SEs of the means. Values were

considered to be significantly different if Po 0.05; NS, not significant.

Treatments: control plots (white bars), plots treated with wood ash plots

(grey bars). A, Anderstorp; P, Perstorp; S, Skogaryd; 0–5, soil depth

0–5 cm; 20–30, soil depth 20–30 cm.

FEMS Microbiol Ecol 73 (2010) 550–562c� 2010 Federation of European Microbiological SocietiesPublished by Blackwell Publishing Ltd. All rights reserved

558 R.G. Bjork et al.

(Weber et al., 1985; Perkiomaki & Fritze, 2002) and com-

munity structure (Frostegard et al., 1993; Baath et al., 1995;

Perkiomaki & Fritze, 2002) in the humus layer. The only

increase in pH in our study was found in Skogaryd, 1 year

after wood ash application. In contrast to other studies, our

data suggest that the microbial biomass (measured as the

amount of PLFA) is influenced by wood ash without causing

any shifts in the microbial community composition.

Twenty-five years after wood ash application, microorgan-

isms seem to have adjusted to the enhanced soil element

concentrations, because no significant effects were recorded

in the top soil (0–5 cm) at Perstorp, although the soil

chemistry was still modified.

In the oligotrophic peatlands, Anderstorp and Perstorp,

the application of wood ash caused decreases in the amounts

of PLFAs and we found corresponding decreases in net N

mineralization. To our knowledge, no net N mineralization

studies have been reported previously from drained organic

soil in relation to wood ash application. However, in a

podzolized sandy soil with Scots pine forest in central

Finland, Fritze et al. (1994) reported no effects on net N

mineralization 2 years after wood ash fertilization (at 1.0, 2.5

and 5.0 tonnes ha�1). In contrast, decreased net N miner-

alization has been observed in the litter layer in Podzols in

coniferous forests in central Sweden, as a result of liming

(Persson et al., 1990). Liming of Podzols seems to affect N

mineralization in the mor layer differently, depending on the

C : N ratio (Nommik, 1979). When the C : N ratio was below

30, liming increased N mineralization, whereas N miner-

alization was decreased when the ratio was above 30

(Nommik, 1979). This is in agreement with the decreases in

N mineralization in Anderstorp and Perstorp, where the

C : N ratios ranged from 31 to 45. The available mineral N

can decrease as a consequence of increased chemical fixation

of NH3 and amino compounds by the SOM, following

increased soil pH (Nommik, 1968; Persson et al., 1990).

However, our study did not show increased pH caused by

wood ash treatments at the oligotrophic sites. For the other

variables measured in our study – NEA and DEA, potential

CH4 oxidation and CH4 production – there were no effects

of wood ash application. These laboratory studies are in

agreement with field measurements of CO2, CH4 and N2O

at Anderstorp, where no effects of wood ash application

were found on any GHG emissions (Ernfors, 2009). Simi-

larly, studies on CH4 production or the methanogenic

community composition in drained peatlands in Finland

found no effect of wood ash application (Jaatinen et al.,

2004; Galand et al., 2005). The N2O emissions from

Anderstorp were very low during most of the year (Ernfors,

2009) and significant annual N2O fluxes from drained

organic forest soils occur usually at a C : N ratio below 25

(Klemedtsson et al., 2005). Even though we found a decrease

in net N mineralization due to decreased net ammonifica-

tion at the oligotrophic sites, both the N2O emissions and

the net nitrification were already at very low levels at these

sites. Further reduction in N availability would therefore

have only minor effects on the N2O emissions from Ander-

storp and on NEA and DEA. However, in a recent study at

the mesotrophic site at Skogaryd, Klemedtsson et al. (in

press) found a decrease in N2O emissions during the winter

Table 4. NEA, DEA, potential CH4 oxidation and CH4 production in experiments Anderstorp (n = 4), Perstorp (n = 4) and Skogaryd (n = 3)

Soil depth (cm)

NEA DEA CH4 oxidation CH4 production

(ng N g�1 OM h�1) (mg N g�1 OM h�1) (mg CH4 g�1 OM h�1) (mg CH4 g�1 OM h�1)

Controlw Wood ashz Control Wood ash Control Wood ash Control Wood ash

Anderstorp

0–5 61.6 28.5 9.98 4.31# 530.8 574.3 6.00 3.92

(21.0) (16.2) (2.72) (0.86) (74.0) (60.2) (2.18) (2.34)

20–30 257.0 169.0 5.22 5.76 1066.4 627.6 1.98 1.48

(155.9) (87.5) (2.30) (3.12) (475.2) (131.4) (1.24) (1.48)

Perstorp

0–5 28.8 39.8 12.36 11.83 191.2 182.4 5.93 10.94

(19.3) (19.1) (1.19) (3.04) (22.5) (31.1) (1.17) (3.19)

20–30 221.9 222.4 1.54 0.40 183.2 218.3 11.70 6.92

(7.7) (30.1) (0.72) (0.40) (11.0) (44.6) (5.43) (0.99)

Skogaryd

0–5 298.6 502.9 1.76 0.99 522.9 567.6 0 0

(65.9) (177.4) (0.61) (0.17) (90.6) (124.5)

20–30 394.9 537.1 0.99 0.45 457.1 540.1 0 0

(70.2) (442.3) (0.75) (0.38) (85.8) (48.2)

Differences between the mean values (� SE) of treatments are denoted by:#Po 0.10.wControl, untreated control.zWood ash, 2.5 tonnes d.w. unknown wood ash ha�1 in Perstorp; 3.3 tonnes d.w. crushed wood ash ha�1 in Anderstorp and Skogaryd.

FEMS Microbiol Ecol 73 (2010) 550–562 c� 2010 Federation of European Microbiological SocietiesPublished by Blackwell Publishing Ltd. All rights reserved

559Wood ash effects on drained forested peatlands

as a consequence of wood ash application. This reduction in

N2O emissions was thought to be an effect of the increased

pH in the top soil, as the enzyme nitrous oxide reductase is

inhibited at a low pH (Knowles, 1982), rather than a

reduction in N availability. Thus, the short time period since

ash application at Skogaryd may explain the observed lack of

response in NEA and DEA. However, the decrease in the rate

of net N mineralization supports the conclusion that the

decrease in the molar amount of PLFA reflects a decrease in

microbial biomass, despite the conflicting results for the

PLFA and SIR levels. Furthermore, the decrease in the

amount of actinobacterial PLFAs and a the corresponding

decrease in net ammonification seen in our study complies

with the fact that actinobacteria play an important role in

the decomposition of more recalcitrant organic materials,

such as cellulose and chitin, and play a vital part in OM

turnover (Alexander, 1999). Thus, our results suggest that

addition of wood ash in drained oligotrophic peatlands

decreases net N mineralization, both in the short term and

in the long term, probably as a result of decreased microbial

biomass.

To conclude, the present study showed that, in oligo-

trophic peatlands, microbial biomass and net N mineraliza-

tion decreased both in the short (4 years) and in the long

term (25 years), without any shifts in the microbial commu-

nity structure. The decreases in microbial biomass contrast

with previous findings in the organic horizons of mineral

soils using similar wood ash doses (Baath & Arnebrant,

1994; Fritze et al., 1994; Baath et al., 1995; Perkiomaki &

Fritze, 2002). These decreases may be linked to the altered

element concentrations in the soil. At the mesotrophic site,

Skogaryd, no effects of wood ash application were found on

microbial processes or community composition, but the

time that had elapsed since the wood ash application was

only 1 year and a longer period may be required before any

effects become apparent. However, Skogaryd also had a

lower C : N ratio than the oligotrophic sites. Therefore, the

responses may differ between mesotrophic and oligotrophic

sites. This study is based on only one sampling occasion;

studies focusing on annual and seasonal variations are

needed to better understand the drivers for microbial

processes and community structure in drained organic soils,

as affected by wood ash application.

Acknowledgements

We thank Mats Bjorkman, Andreas Karlsson and Gustaf

Laggren for their assistance in the field and laboratory.

Furthermore, we are grateful to two anonymous reviewers

for valuable referee comments. The Thermal Engineering

Research Institute (grant no Q6-666 to L.K.) supported this

work and is gratefully acknowledged. The work was also

conducted with financial support from the NitroEurope IP

under the EC 6th Framework Programme (contract no.

017841), the Tellus research program dedicated to Earth

Systems Science, Gothenburg University and the Swedish

Research Council for Environment, Agricultural Sciences

and Spatial Planning.

References

Alexander DB (1999) Bacteria and archaea. Principles and

Applications of Soil Microbiology (Sylvia DM, Fuhrmann JJ,

Hartel PG & Zuberer DA, eds), pp. 44–71. Prentice Hall,

Englewood Cliffs, NJ.

Anderson JPE & Domsch KH (1978) A physiological method for

the quantitative measurement of microbial biomass in soils.

Soil Biol Biochem 10: 215–221.

Augusto L, Bakker MR & Meredieu C (2008) Wood ash

applications to temperate forest ecosystems – potential

benefits and drawbacks. Plant Soil 306: 181–198.

Baath E & Arnebrant K (1994) Growth rate and response of

bacterial communities to pH in limed and ash treated forest

soil. Soil Biol Biochem 26: 995–1001.

Baath E, Frostegard A, Pennanen T & Fritze H (1995) Microbial

community structure and pH response in relation to soil

organic matter quality in wood-ash fertilized, clear-cut or

burned coniferous forest soils. Soil Biol Biochem 27: 229–240.

Bergman I, Svensson BH & Nilsson M (1998) Regulation of

methane production in a Swedish acid mire by pH,

temperature and substrate. Soil Biol Biochem 30: 729–741.

Bjurstrom H, Ilskog E & Berg M (2003) Askor fran biobranslen

och blandbranslen – mangder och kvalitet. The Swedish

Energy Agency, ER 10 (in Swedish with English summary).

Bjork RG, Klemedtsson L, Molau U, Harndorf J, Odman A &

Giesler R (2007) Linkages between N turnover and plant

community structure in a tundra landscape. Plant Soil 294:

247–261.

Bramryd T & Fransson B (1995) Silvicultural use of wood ashes –

effects on the nutrient and heavy metal balance in a pine

(Pinus sylvestris L.) forest soil. Water Air Soil Poll 85:

1039–1044.

Demeyer A, Nkana JCV & Verloo MG (2001) Characteristics of

wood ash and influence on soil properties and nutrient uptake:

an overview. Bioresource Technol 77: 287–295.

Ernfors M (2009) Greenhouse gas fluxes between drained

forested peatlands and the atmosphere. PhD Thesis, University

of Gothenburg, Sweden.

EU (2007) Renewable energy road map – renewable energies in

the 21st century: building a more sustainable future.

Communication from the Commission to the Council and the

European Parliament, Commission of the European

Communities, Com (2006) 848.

Fritze H, Smolander A, Levula T, Kitunen V & Malkonen E

(1994) Wood ash fertilization and fire treatments in Scots pine

forest stand: effects on the organic layer, microbial biomass

and microbial activity. Biol Fert Soils 17: 57–63.

FEMS Microbiol Ecol 73 (2010) 550–562c� 2010 Federation of European Microbiological SocietiesPublished by Blackwell Publishing Ltd. All rights reserved

560 R.G. Bjork et al.

Frostegard A & Baath E (1996) The use of phospholipid fatty acid

analysis to estimate bacterial and fungal biomass in soil. Biol

Fert Soils 22: 59–65.

Frostegard A, Baath E & Tunlid A (1993) Shifts in the structure of

soil microbial communities in limed forests as revealed by

phospholipid fatty acid analysis. Soil Biol Biochem 25:

723–730.

Galand PE, Juottonen H, Fritze H & Yrjala K (2005) Methanogen

communities in a drained bog: effect of ash fertilization.

Microb Ecol 49: 209–217.

Holmberg SL & Claesson T (2001) Mineralogy of granulated

wood ash from a heating plant in Kalmar, Sweden. Environ

Geol 40: 820–828.

Jaatinen K, Knief C, Dunfield PF, Yrjala K & Fritze H (2004)

Methanotrophic bacteria in boreal forest soil after fire. FEMS

Microbiol Ecol 50: 195–202.

Jokinen HK, Kiikkila O & Fritze H (2006) Exploring the

mechanisms behind elevated microbial activity after wood ash

application. Soil Biol Biochem 38: 2285–2291.

Karltun E, Saarsalmi A, Ingerslev M, Mandre M, Andersson S,

Gaitnieks T, Ozolincius R & Varnagiryte-Kabasinskiene I

(2008) Wood ash recycling – possibilities and risks. Sustainable

Use of Forest Biomass for Energy: A Synthesis with Focus on the

Baltic and Nordic Region (Roser D, Asikainen A, Raulund-

Rasmussen K & Stupak I, eds), pp. 79–108. Springer

Science1Business Media B.V., Dordrecht, the Netherlands.

Klemedtsson L, Svensson BH, Lindberg T & Rosswall T (1977)

The use of acetylene inhibition of nitrous oxide reductase in

quantifying denitrification. Swed J Agr Res 7: 179–185.

Klemedtsson L, Kasimir-Klemedtsson A, Moldan F & Weslien P

(1997) Nitrous oxide emission from Swedish forest soils in

relation to liming and simulated increased N-deposition. Biol

Fert Soils 25: 290–295.

Klemedtsson L, von Arnold K, Weslien P & Gundersen P (2005)

Soil CN ratio as a scalar parameter to predict nitrous oxide

emissions. Glob Change Biol 11: 1142–1147.

Klemedtsson L, Ernfors M, Bjork RG, Weslien P, Rutting T, Crill P

& Sikstrom U (in press) Reduction of greenhouse gas

emissions by wood ash application to a Picea abies forest on a

drained organic soil. Eur J Soil Sci.

Knowles R (1982) Denitrification. Microbiol Rev 46: 43–70.

Kroppenstedt RM (1985) Fatty acids and menaquinone analysis

of actinomycetes and related organisms. Chemical Methods in

Bacterial Systematics (Goodfellow M & Minnikin DE, eds), pp.

173–199. Academic Press, London.

Lensi R, Gourbiere F & Josserand A (1985) Measurement of small

amounts of nitrate in an acid soil by N2O production. Soil Biol

Biochem 17: 733–734.

Lensi R, Mazurier F, Gourbiere F & Josserand A (1986) Rapid

determination of the nitrification potential of an acid forest

soil and assessment of its variability. Soil Biol Biochem 18:

239–240.

Lin Q & Brookes PC (1999) An evaluation of the substrate-

induced respiration method. Soil Biol Biochem 31: 1969–1983.

Magnusson T & Hanell B (1996) Aska till skog pa torvmark –

Ramprogram Askaterforing. NUTEK Report, 85, NUTEK

Forlag, Stockholm (in Swedish with English summary).

Makiranta P, Laiho R, Fritze H, Hytonen J, Laine J & Minkkinen

K (2009) Indirect regulation of heterotrophic peat soil

respiration by water level via microbial community structure

and temperature sensitivity. Soil Biol Biochem 41: 695–703.

Maljanen M, Nykanen H, Moilanen M & Martikainen PJ (2006)

Greenhouse gas fluxes of coniferous forest floors as affected by

wood ash addition. Forest Ecol Manag 237: 143–149.

Maljanen M, Sigurdsson BD, Gujmundsson J, Oskarsson H,

Huttunen JT & Martikainen PJ (2009) Land-use and

greenhouse gas balances of peatlands in the Nordic countries –

present knowledge and gaps. Biogeosciences Discuss 6:

6271–6338.

Moilanen M, Silfverberg K, Hokka H & Issakainen J (2004)

Comparing effects of wood ash and commercial PK fertilizer

on the nutrient status and stand growth of Scots pine on

drained mires. Baltic For 10: 2–10.

Moilanen M, Silfverberg K, Hokka H & Issakainen J (2005) Wood

ash as a fertilizer on drained mires – growth and foliar

nutrients of Scots pine. Can J Forest Res 35: 2734–2742.

Moore TR & Dalva M (1997) Methane and carbon dioxide

exchange potentials of peat soils in aerobic and anaerobic

laboratory incubations. Soil Biol Biochem 29: 1157–1164.

Nommik H (1968) Nitrogen mineralization and turnover in

Norway Spruce (Picea abies (L.) Karst.) raw humus as

influenced by liming. 9th International Congress of Soil Science,

Transactions, Vol. II, pp. 533–545.

Nommik H (1979) The future role of liming in forestry. Skogs-och

Lantbruksakademiens Tidskrift, suppl 13, pp. 31–37 (in

Swedish with English summary).

Nordgren A (1988) Apparatus for the continuous long-term

monitoring of soil respiration rate in large numbers of

samples. Soil Biol Biochem 20: 955–958.

Nordgren A (1992) A method for determining microbially

available nitrogen and phosphorus in an organic soil. Biol Fert

Soils 13: 195–199.

Økland RH, Økland T & Rydgren K (2001)

Vegetation–environment relationships of boreal spruce swamp

forest in Østmarka Nature Reserve, SE Norway. Sommerfeltia

29: 1–190.

Paavilainen E & Paivanen J (1995) Peatland Forestry – Ecology and

Principles. Ecological Studies, Vol. 111. Springer-Verlag, Berlin.

Pahlsson L (1998) Vegetation types of the Nordic Countries. Nordic

Council of Ministers, TemaNord, 510, Copenhagen.

Payton ME, Miller AE & Raun WR (2000) Testing statistical

hypotheses using standard error bars and confidence intervals.

Commun Soil Sci Plan 31: 547–551.

Payton ME, Greenstone MH & Schenker N (2003) Overlapping

confidence intervals or standard error intervals: what do they

mean in terms of statistical significance? J Insect Sci 34: 1–6.

Perkiomaki J & Fritze H (2002) Short and long term effects of

wood ash on the boreal forest humus microbial community.

Soil Biol Biochem 34: 1343–1353.

FEMS Microbiol Ecol 73 (2010) 550–562 c� 2010 Federation of European Microbiological SocietiesPublished by Blackwell Publishing Ltd. All rights reserved

561Wood ash effects on drained forested peatlands

Persson T, Wiren A & Andersson S (1990) Effects of liming on

carbon and nitrogen mineralization in coniferous forests.

Water Air Soil Poll 54: 351–364.

Rinnan R & Baath E (2009) Differential utilization of carbon

substrates by bacteria and fungi in tundra soil. Appl Environ

Microb 75: 3611–3620.

Robertsson GP, Wedin D, Groffman PM, Blair JM, Holland EA,

Nadelhoffer KJ & Harris D (1999) Soil carbon and nitrogen

availability: nitrogen mineralization, nitrification and soil

respiration potentials. Standard Soil Methods for Long-Term

Ecological Research (Robertson GP, Coleman DC, Bledsoe CS &

Sollins P, eds), pp. 106–114. Oxford University Press, New

York.

Saarsalmi A, Malkonen E & Piirainen S (2001) Effects of wood

ash fertilization on forest soil chemical properties. Silva Fenn

35: 355–368.

Saarsalmi A, Malkonen E & Kukkola M (2004) Effects of wood

ash fertilization on soil chemical properties and stand nutrient

status and growth of some coniferous stands in Finland. Scand

J Forest Res 19: 217–233.

Sikstrom U, Bjork RG, Ring E, Ernfors M, Jacobson S, Nilsson

MB & Klemedtsson L (2009) Tillforsel av aska i skog pa dikad

torvmark i sodra Sverige – effekter pa skogsproduktion, floden

av vaxthusgaser, torvegenskaper, markvegetation och

grundvattenkemi. Thermal Engineering Research Institute

Report No. 1109 (in Swedish with English summary).

Sikstrom U, Almqvist C & Jansson G (in press) Growth of Pinus

sylvestris after addition of ash or PK on a peatland in southern

Sweden. Silva Fenn, in press.

Silvola J, Valijoki J & Aaltonen H (1985) Effect of draining and

fertilization on soil respiration at three ameliorated peatland

sites. Acta For Fenn 191: 1–32.

Smith MS & Tiedje JM (1979) Phases of denitrification following

oxygen depletion in soil. Soil Biol Biochem 11: 261–267.

Steenari BM, Karlsson LG & Lindqvist O (1999) Evaluation of the

leaching characteristics of wood ash and the influence of ash

agglomeration. Biomass Bioenerg 16: 119–136.

Succow M & Joosten H (eds) (2001) Landschaftsokologische

Moorkunde, 2nd edn. Schweizerbart, Stuttgart.

Sundh I, Nilsson M, Granberg G & Svensson BH (1994) Depth

distribution of microbial production and oxidation of

methane in northern boreal peatlands. Microb Ecol 27:

253–265.

Susyan EA, Ananyeva ND & Blagodatskaya EV (2005) The

antibiotic-aided distinguishing of fungal and bacterial

substrate-induced respiration in various soil ecosystems.

Microbiology 74: 336–342.

Tamm CO (1991) Nitrogen in Terrestrial Ecosystems. Springer-

Verlag, Berlin.

Vance ED (1996) Land application of wood-fired and

combination ashes: an overview. J Environ Qual 25:

937–944.

Weber A, Karsisto M, Leppanen R, Sundman V & Skujins J (1985)

Microbial activities in a histosol: effects of wood ash and NPK

fertilisers. Soil Biol Biochem 17: 291–296.

Zak DR, Ringelberg DB, Pregitzer KS, Randlett DL, White DC &

Curtis PS (1996) Soil microbial communities beneath Populus

grandidentata grown under elevated atmospheric CO2. Ecol

Appl 6: 257–262.

FEMS Microbiol Ecol 73 (2010) 550–562c� 2010 Federation of European Microbiological SocietiesPublished by Blackwell Publishing Ltd. All rights reserved

562 R.G. Bjork et al.